The figure above is a diagram of the system wiring. Data flows from
the satellite dish through the communications room, to the final products
that are distributed through the MBARI network. Detailed description of
each of the components is below.

Satellite Dish

The Satellite dish is a "Tiris" model THRPT-6 1.5 meter dish manufactured
by Telonics Corp. The owners
manual for this can be found in Office number 256, on the bookshelf to
the right of the door. This is a completely self contained unit,
receiving all power and commands from the control unit in the communications
room. Although this is a very low maintenance system, after 3 to
5 years, the gear box may begin to wear out and need replacement. The indicator
for this is that the antennae will not move smoothly but will "jump" along
its positioning path.

Controller

The Satellite control system is a set of hardware that includes FOAM, the
THRPT antenna controller, and a BNC box. FOAM keeps track of which
satellites to track and download data from. FOAM does this by retrieving
the satellite overpass times and orbital elements from an ftp server (ftp.cerf.net)
each day at 8:34 AM local. When a satellite comes into view of the
antenna, FOAM starts the antennae controller in the Telonics SCSI box,
tracks the satellite, and starts the flow of data. Azimuth and altitude
antenna motor control is accomplished with the Telonics THRPT 6S Antenna
controller. The control box provides power and directional control
to the antenna motors from within the control room, thus eliminating the
need for a power source or control hardware outside with the antenna. Satellite
data from the antenna then flows through the BNC cable and BNC adapter
box to SCSI box.

Telonics PC

The previous system incorporated a PC that managed the antennae control.
This was replaced by the Telonics SCSI box in late 1999. The description
is left here for reference.

The Telonics PC is an HP Vectra 486/66 that communicates with FOAM via
the recorder cable and the MBARI network. A critical maintenance
component of this system is the PC clock. The PC clock controls the
timing of the antenna controller and needs to be maintained within one
or two seconds of accuracy. This clock wanders over time and should be
checked every week. Data flowing in from the antenna flows into the PC
which then feeds SeaWiFS data to the Orbital Sciences Ground Processor
for decoding and AVHRR data directly to FOAM.

Foam workstation

Foam is an HP UNIX workstation that serves as the main component of the
MBARI satellite control system. Foam retrieves and maintains the satellite
orbital elements, ingests the raw data from the SCSI box, generates
and distributes data products, and stores raw data to tape. The main process
of foam can be seen by looking at the two windows that should be running
on the Foam monitor at all times. These windows, are labeled HRPTDI, and
HRPTDP. The acronym HRPT stands for High Resolution Picture Transmission,
while the last two letters describe tasks performed in each window. These
tasks are explained below:

HRPTDI "Data Ingestion"

The Data Ingestion window on foam shows the order, the type, the start
time, the duration and the status of the satellites to receive data from.
The order of processing proceeds from the bottom of the screen to the top.
The first column is the platform; noaac is AVHRR on NOAA-12, noaae is AVHRR
on NOAA-14, and obv2 is the SeaWiFS sensor on SeaStar. The next column
is the date field in the format YYDDDDHHMMSS. The third field is the duration
in minutes of the pass. The last part of the line describes the status
of the pass.

In the example below, the bottom line shows "off-line" . The "off-line"
denotes that the system locked on to the satellite and received data. There
is no evidence however that the data was backed up as planned The
next line up shows "off-line off-line". Again the first "off-line" denotes
that the system was successful in getting the data, and the second "off-line"
denotes that the data was backed up to tape and is being stored. On the
third line from the bottom, a pass is being processed. This is shown logically
by "on-line (processing)". When the processing is complete, the screen
will change to "off-line" or "off-line off-line" depending on the success
of the operation. The top line indicates the next satellite to be received.
"on Thurs., Feb. 19 at 18:45:34 (local)" Come back then and see it all
run!

Example:

obv2 99049211055 1045 on Thurs., Feb., 19 at 18:45:34 (local)

noac 99049193323 1010 on-line (processing)

noae 99049151029 1127 off-line off-line (19)

noae 99049133018 1211 off-line on-line (19)

HRPTDP "Data Production"

The Data Production window, handles the tape backup, the conversion
of raw telemetry to L0 data, and AVHRR data products. When this window
fails, the passes in the HRPTDI window will not have the (19) at
the end, nor will they write "off-line" to tape. Restarting this window
requires restarting the whole process. The system will then automaticaly
start to process all of the unprocessed data (those not marked with 19)
and attempt to write the raw files to tape. Due to the fact that
processing takes less time than tape writing, not all of the passes will
be written to tape. Check back after an hour or so to write the unwriten
passes to tape manualy.

Logins and ASAPs

Right clicking on the mouse produces a pop up menu that allows new logins
and ASAP's. Logins are Root, GAE, HRPT, and FORCAST. Root is reserved for
systems administrators, GAE and FORECAST are logins for the Orbital Imaging
System 9000 software. HRPT is the preferred login used for system maintenance.
Selecting ASAP brings up a second pop up list that will re-start the HRPTDI
process described above. This was once useful because the system had the
hobby of dropping the Data Ingestion window.

Tape Back up system

The tape backup system is a 4mm tape installed in the FOAM chassy. These
tapes are capable of holding about 3 days of SeaWiFS Data and hence must
be changed regularly. Click here for instructions on how to maintain the
tape
system

Data Path

The links below will produce diagrams that follow the data path from raw
satellite telemetry through to the final data products.

Lepas Workstation

The Lepas workstation is an SGI with dual 180Mhz processors. This is
a dedicated computer that contains the SeaDas and IDL programs, the image
processing scripts, and an extensive file structure for archiving the data.